Thermal Transfer Device with Reduced Vertical Profile

ABSTRACT

A thermal transfer device having a reduced vertical profile. The device includes a condenser with substantially vertical internal cooling fins. An inlet conducts a thermal transfer fluid in a vapor state to the tops of the cooling fins where the vapor condenses and flows down the fins to the bottom of the condenser. The bottom of the condenser is angled towards an outlet for conducting the liquid thermal transfer fluid to a reservoir for holding the fluid. The inlet and the outlet are both positioned at a height above the level of the thermal transfer fluid in liquid state in the reservoir. The device may also include fins on the exterior of the condenser for providing cooling surfaces which do not contact the thermal transfer fluid in either the liquid or vapor states.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is directed to a thermal transfer device, such as a closed loop fluid cooling system having at least one evaporator, at least one condenser and one or more fluid conduits connecting the evaporator and condenser for use in indirectly cooling objects with a cooling fluid and, more particularly, to a thermal transfer device having a reduced vertical profile for conducting a cooling fluid into indirect thermal contact with an object to be cooled in a compact environment.

2. Description of the Related Art

Passive closed loop two-phase fluid cooling systems are well-known thermal transfer devices used for cooling objects that generate excessive heat, such as, without limitation, computer chips. The term passive is meant to denote a system which uses no mechanized pump to circulate the cooling fluid. The motivation for the fluid to circulate in a passive system comes from buoyancy changes and phase changes in the fluid as heat is added. The evaporator is generally placed in thermal contact with the object to be cooled, and a cooling fluid in liquid form is passed over a surface which separates the liquid from the actual object to be cooled. In this fashion, heat may be transferred between the fluid and the object, without the fluid ever coming into direct contact with the object. The addition of heat to the fluid causes at least a portion of the fluid to vaporize. The vapor is then conveyed to the condenser. Heat is released as the vapor re-condenses to a liquid state. The condensed liquid is returned to the evaporator and the vaporization-condensation cycle repeats. FIG. 1 a depicts such a prior art condenser 100, and FIG. 1 b shows a detail thereof. Prior art condensers commonly use tubes 102 of circular cross section, or flattened tubes which approximate an oval or rectangular cross section, to provide the condensation surfaces. These tubes are typically disposed with their longitudinal axis vertical. A multitude of air cooling fins 104 with apertures dimensioned to fit the perimeters of these tubes are arranged horizontally. Note that in the prior art condenser 100 of FIG. 1 the air cooling fins 104 are interspersed with the condenser tubes and as such the air cooling fins and condenser tubes occupy the same vertical region above the liquid header tank 106 and below the vapor header tank 108. A vapor conduit 110 conducts heated vapor to vapor header tank 108 and a condensate return line 112 returns liquid condensate 114 to a reservoir 116.

This prior art configuration thus requires that all of the air cooling fins 104 are located above the collection point for the condensed fluid (condensate 114), specifically, above the liquid header tank 106. This is the single biggest limitation of the prior art condenser. This limitation of the prior art condenser can best be illustrated by comparing FIG. 1 to FIG. 2 which depicts the instant invention. In FIG. 2 it can be seen that air cooling fins 118 are located above and below the region of the condenser chamber. Although

FIG. 2 depicts air cooling fins 118 both above and below the region of the condenser chamber 120 it should be understood that the air cooling fins 118 could be placed either above or below the condenser chamber 120. The air cooling fins 118 are not interspersed with the condenser fins (within condenser 120, and not shown in FIG. 2). This means that the condenser fins need not be spaced as far apart from each other horizontally as in the prior art's design as they need not pass cooling air between them. This in turn means that although the condenser fins of the instant invention are shorter along their vertical axis than the prior art design, their closer horizontal spacing allows for more fins to be used and therefore for a total condensate surface area substantially equal to the prior art design. The instant invention can likewise be configured to provide a total air cooling fin area substantially equal to the prior art design. The key benefit of the invention is that the collection point for the condensed fluid (liquid condensate 114) is located substantially higher than that of the prior art design. This key benefit of the invention, the ability to locate the condensate surface area and the collection point for the condensed liquid high in the space available and well above the level of the evaporator component, is most apparent in the embodiment of FIG. 4. Referring again to FIG. 1, the difference between the height of liquid in the reservoir (RH) and the height of fluid in the condenser (CH) is the gravitational height (GH), sometimes referred to as gravitational head. As can be seen in the Figures, GH-2 of FIG. 2 is substantially larger that GH-1 of FIG. 1. The ability of each design to return condensate from the condenser to the reservoir is directly tied to their respective gravitational heights, GH-1 and GH-2. Where, for a given available height (AH), both the prior art design and the invention can be configured to have substantially equal air cooling fin area and internal condenser surface area, the invention can operate at a higher heat load by virtue of its higher GH. This is because the mass transport rate of condensate return is directly related to the maximum amount of heat transfer achievable.

To further illustrate the advantage of the invention over the prior art design refer again to FIG. 3. FIG. 3 depicts a prior art type design configured to provide the same gravitational height as with the invention (GH-2). As can be seen in FIG. 3, this configuration provides for substantially less vertical space for the air cooling fins and condenser tubes as there is a region 122 below the condenser that cannot be used. The reduction in air cooling fin area and condenser tube area renders this configuration inferior to the invention.

For the reasons recited above, the invention can transfer a higher heat load compared to condensers of the prior art design in applications demanding a relatively low available height (AH), i.e., “low profile” designs.

There are examples of prior art type condensers that have been re-oriented to achieve a low profile but these typically accomplish a low profile at the expense of another significant design consideration.

For example, U.S. Pat. No. 7,422,052 discloses a low profile cooling system with a substantially horizontally disposed condenser component. The condenser is generally similar to prior art vertical, or standing, condensers, except that it is angled closer to the horizontal while still at a shallow incline. This provides the benefit of a reduced vertical profile, at the expense of a substantially increased horizontal profile.

U.S. Pat. No. 7,231,961 also discloses a low profile cooling system. This reference specifies a condenser as “a long chamber having a narrow interior channel”. This chamber is oriented with its “long” dimension oriented substantially parallel to the horizontal plane where the horizontal plane is taken to mean the plane on which the device to be cooled is mounted, e.g., the plane of a circuit board bearing the chip/processor to be cooled. One side of this chamber (a substantially vertical exterior surface) is populated with air cooling fins. Based on the dimensional ranges recited, which define the length, width and height of this chamber, one could describe the chamber as simply a singular condenser tube, much like many of the condenser tubes described earlier with reference to prior art condensers. In this case, the singular condenser tube is disposed with its longitudinal axis horizontal instead of vertical. As such, the design achieves a low vertical profile simply by placing the condenser tube in a horizontal configuration. This is done clearly at the expense of gravitational height. This limitation is expressly recited in column 5, lines 12-19;

“Typically, the condensers of thermosyphons are placed over or higher than the evaporators to utilize gravity to force the liquid from the condenser to the evaporator. This placement is not possible in spaces where the available height is severely limited. Although part of the condenser may be higher than the evaporator, or vice versa, the condenser and evaporator are approximately horizontal to each other in the present invention.”

It should also be pointed out that this prior art design requires a significant portion of the internal volume of the condenser to be occupied by standing liquid.

This represents a well know limitation on the performance of a condenser in that no condensation can occur on condenser surfaces embedded in standing liquid, a situation often referred to as “flooding of the condenser”.

Accordingly, although condensers are generally well known and widely used, there is a continuing need to make condensers more efficient, and, therefore, more competitive, cost-effective and useful. It is especially useful to provide a condenser that can be used for cooling an object in a very compact environment while providing adequate internal condenser surface area coupled with adequate gravitational height for transport of the condensate.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a thermal transfer device which provides efficient and effective cooling of objects which may tend to overheat, such as computer chips.

It is a further object of the invention to provide an improved thermal transfer device having a reduced vertical profile for use in applications where there is limited vertical clearance or headroom.

In accordance with these and other objects of the invention there is provided a thermal transfer device which includes a chamber having substantially vertical condenser fins for condensing a heated thermal transfer fluid from vapor to liquid. The chamber has an inlet for receiving the vapor and an outlet for conducting the condensed fluid in its liquid state back to a reservoir. The inlet and the outlet are both positioned at a level higher than the level of the liquid thermal transfer fluid in the reservoir. The vertical condenser fins which provide the condensing surfaces are positioned substantially in the vertical space between the inlet and the outlet. The benefit of this arrangement is that it leaves a larger portion of the available vertical height for gravitational return of the condensate to the evaporator. This arrangement likewise allows for a significant change in the height of the liquid in the liquid return line without the negative consequence of driving liquid into the condenser component (which, if it occurs, renders some portion of the condenser inoperative). This structure permits the device to achieve good condensation performance and have an overall reduced vertical profile. Additionally, this structure permits the device to have an overall reduced vertical profile in which the depth of the chamber is greater than the height of the interior of the chamber.

In preferred embodiments of the invention, the condenser fins within the chamber may include flutes on their surfaces to increase the effective cooling surface within the chamber. The flutes may be disposed in matched opposed pairs on opposed sides of the fins, or may be staggered in alternation on opposing sides as a matter of design choice. As typically applied to the cooling of electrical apparatus or electronic apparatus one or more of the external surfaces of the chamber will be fitted with a multitude of air cooling fins in thermal communication with the chamber. The surfaces employed are most typically the top or bottom surface. Although a multitude of fins (sometimes referred to as an array of fins) are most commonly employed, a singular fin can be used as well. Air is passed over the air cooling fin or fins either by natural convection means or by forced convection means. Designing, fabricating and employing air cooling fins for use in natural or forced convection cooling is well known in the art of cooling system design. As an alternative to the use of one or more air cooling fins, a liquid cold plate can be placed on either the top surface or bottom surface of the chamber, or both. Used in this manner, a cold plate will be fixed to the chamber in so as to be in thermal communication with the chamber. A cooling fluid is circulated through the cold plate. The cooling provided by the cooling fluid causes the vapor inside the chamber to condense. The term “Liquid Cold Plate” is interchangeable with “Liquid Cooled Heat Sink” and both terms are well known in the art. An example of a liquid cooled heat sink is disclosed in U.S. Pat. No. 5,829,516 and is herein incorporated by reference.

Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further description of the invention, reference is made to the exemplary embodiments shown in the drawings, in which like numerals refer to like parts.

FIGS. 1 a and 1 b are a schematic illustration of a prior art thermal transfer device;

FIGS. 2 a and 2 b are a schematic illustration of the inventive thermal transfer device;

FIGS. 3 a and 3 b are a schematic illustration of a prior art thermal transfer device configured with the condenser elevated above the surface on which the evaporator sits;

FIGS. 4 a and 4 b are a schematic illustration of the preferred embodiment of the inventive thermal transfer device configured for operation in low vertical profile applications;

FIG. 5 is a schematic illustration of a chamber used in a first embodiment of the inventive thermal transfer device;

FIG. 6 a is a schematic illustration of a secondary embodiment of the chamber used in the inventive thermal transfer device;

FIG. 6 b is a schematic illustration of a tertiary embodiment of the chamber used in the inventive thermal transfer device;

FIG. 7 is a perspective view of the thermal transfer device of FIG. 4 showing a multitude of air cooled fins attached to the bottom of the condenser chamber, with arrows depicting cooling air traversing the air cooled fins;

FIG. 8 is a perspective view of the condenser component of the thermal transfer device of FIG. 4 with a cut-away in the top of the chamber to allow viewing of internal structure;

FIGS. 9 a and 9 b are cross-sections of differing embodiments of fins and flutes used in the inventive thermal transfer device;

FIG. 10 is a schematic cross-section of a single tube embodiment of the inventive thermal transfer device;

FIG. 11 is a perspective view of a further embodiment of the inventive thermal transfer device with a liquid cooled heat sink, also known as a liquid cold plate, placed in thermal communication with lower external surface of condenser chamber, with arrows depicting cooling fluid entering and leaving the liquid cold plate;

FIGS. 12 a, 12 b and 12 c are schematic illustrations of the preferred embodiment of the invention mounted on a circuit board and further comprising a bulkhead to separate the region of the circuit board from the region of the condenser component;

FIG. 13 a is a schematic illustration of the condenser component of the inventive thermal transfer device where the condenser chamber is shown in cross-section and the condenser chamber is located in vertical region B, entirely above vertical region A where one array of air cooling fins is located; and

FIG. 13 b is a schematic illustration of the condenser component of the inventive thermal transfer device where the condenser chamber is shown in cross-section and the condenser chamber is located in vertical region B, substantially above vertical region A where one array of air cooling fins is located.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

In accordance with a preferred embodiment of the invention there is shown, generally at 10 in FIG. 4, a thermal transfer device, or “closed loop fluid cooling system” in accordance with the invention. Thermal transfer device 10 includes a reservoir 12 acting as an evaporator, for holding a thermal transfer fluid 14, a first conduit 16 for conducting thermal transfer fluid 14 out of reservoir 12 when the thermal transfer fluid is in a vapor state, and a second conduit 18 for conducting thermal transfer fluid 14 back to reservoir 12 once thermal transfer fluid 14 has condensed from its vapor state to a liquid state. The maximum height to which the liquid portion of the thermal transfer fluid can rise before flooding the condensing surfaces is denominated as h in FIG. 4.

In the preferred embodiment, thermal transfer fluid 14 is water or deionized water. Where a design places specific requirements on the cooling fluid, e.g., freeze tolerance, corrosion resistance or that the cooling fluid be electrically non-conductive, organic cooling fluids such as alcohols, refrigerants such as R134A or engineered fluids such as 3M Fluorinert or Novec Liquids may be used.

Thermal transfer device 10 also includes a chamber 20, acting as a condenser, having an inlet 22 (FIG. 7) coupled to first conduit 16 and an outlet 24 coupled to second conduit 18. In the preferred embodiment, chamber 20 is hermetic and made of metal, such as aluminum or copper.

FIGS. 5 and 8 show one of a plurality of substantially vertical condenser fins 26 positioned within chamber 20 to provide cooling surfaces for thermal transfer fluid 14 to condense from its vapor state when it is introduced to chamber 20 to its liquid state for return to reservoir 12. Fins 26 are spaced from one another to form passages therebetween through which thermal transfer fluid 14 may flow, and contact more of the surfaces of cooling fins 26. To facilitate the distribution of vapor along all passages, a first open header space 32 (FIGS. 5 and 6 a) is provided at the top of chamber 20. First open header space 32 spans substantially the entire width of chamber 20, which permits the unimpeded flow of thermal transfer fluid 14 in a vapor state over the entire width of chamber 20, and then along the passages to the entire depth of chamber 20. (Depth, width and height orientations are shown in FIG. 8.) Allowing the smooth distribution of the vapor to the entire depth and width of 20 exposes the maximum cooling surface area of cooling fins 26 in a most efficient manner.

To facilitate the return flow of thermal transfer fluid 14 to reservoir 12, a second open header space 34 is provided. Second open header space extends substantially the entire width of chamber 20 and opens into outlet 24. Although in the proffered embodiment of the invention two open header spaces are provided, a singular contiguous header space (illustrated as 33 in FIG. 6 b) can be used as a matter of design choice as the higher density of the condensate (compared to the vapor) will lead to the condensate naturally collecting in the lower portion of the singular header space leaving the upper portion available for the vapor.

Inlet 22 may either be positioned in the top of chamber 20, as shown in FIGS. 5 and 6 b, or in the side of chamber 20 as shown in FIG. 6 a. In either configuration, the vapor of thermal transfer fluid 14 will enter first header space 32, and condense on fins 26 as described. The choice of construction is a mere matter of design choice and will depend upon the requirements of the application, and the selection of the appropriate position for inlet 22 is well within the skill of one of ordinary skill in the art.

The structural arrangement of the present invention allows for all of the condensing surfaces to be located gravitationally above the liquid level in both the reservoir and the liquid return conduit. This structure provides the further benefit that the condensing surfaces, together with the chamber housing them, occupy a relatively small portion of the vertical height available for the entire thermal transfer device.

FIG. 7 shows an embodiment of the invention in which air cooled fins 30′ are attached to the bottom external surface of the condenser chamber. Alternatively, a liquid-cooled cold plate 30 as shown in FIG. 11, or any other known method of providing cooling to condenser, can be used in place of the air cooled fins.

A further possibility for improving the performance of thermal transfer device 10 is to provide fins 26 with flutes 40, as shown in FIGS. 9 a and 9 b. Flutes 40 may be either positioned as matched pairs on opposing sides of fins 26 (FIG. 9 a) or in a staggered arrangement as shown in FIG. 9 b, as a matter of design choice.

It is also possible to realize the benefits provided by the invention by use of a single port 36 as both an input and an output, as shown in FIG. 10, as a matter of design choice. In single port 36, vapor 42 may flow upwards while liquid 44 may flow down.

In another embodiment of the invention shown in FIG. 12, a thermal transfer device 40, together with the microprocessor being cooled is mounted on a circuit board. The circuit board, which includes an electrical connector 42 disposed near one of its peripheral edges, can be inserted into another structure such as a slot within a computer chassis. Thermal transfer device 40 bears a liquid cold plate 44 which provides the cooling means for condenser 20 as well as an electrical connector 46 dimensioned to mate with electrical connecter 42 on the circuit board. Arranged as such, when the circuit board is inserted in the chassis, electrical connectors 42, 46 mate with each other and condenser 20 mates with liquid cold plate 44. The mating between condenser 20 and liquid cold plate 44 must provide good thermal communication between the two components in order to transfer heat efficiently, for this reason an interface material 48 to promote thermal transfer such as a thermal grease or gel, or a thermal interface pad is placed between the mating surfaces. In typical practice, solid/non-grease interface materials such as graphite-based pads are permanently fixed to the surface of one component by means of an adhesive. The surface without adhesive contacts the other component. This allows the two components to be assembled or “mated” and disassembled repeatedly without damage to the interface material. The cooling fluid circulating through the liquid cold plate 44 can be provided by a number of means well known in the art of cooling of servers, mainframe computers and telecom equipment. Two specific examples are as follows; [1] a dedicated stand-alone chiller can provide the cooling fluid, typically de-ionized water at a pre-determined temperature and at a pre-determined volumetric flow rate. The temperature of the liquid entering the cold plate is set according to the desired maximum operating temperature of the microprocessor being cooled. The volumetric flow rate of the cooling fluid is set according to the total amount of wattage that needs to be transferred and by the maximum desired temperature rise of the cooling fluid within the liquid cold plate. The determining of set points for both of these parameters, cooling fluid temperature entering the cold plate, and volumetric flow rate of the cooling fluid, can be accomplished with well known and long standing engineering methods and would not require an undue amount of experimentation. Alternatively, [2] the building facility housing the equipment being cooled, for example, a data center housing and supporting many servers, could provide cooling water at a sufficient volumetric flow rate at a pre-determined temperature and pressure. This is sometimes referred to as “utility water”. Designing the liquid cold plate based on these values to achieve the thermal transfer required can, as in the previous example, be accomplished with well known and long standing engineering methods.

The advantage of this embodiment is that a fluid cooled electronic component such a chip or micro processor together with the circuit board on which it is mounted can be removed for repair or replacement without disturbing the plumbing providing cooling fluid to, or removing cooling fluid from, the liquid cold plate component. This in turn lowers the risk of using water to indirectly cool an electronic component in that in normal operation, including service and maintenance, there is less risk of cooling water escaping and damaging the electronic components. This benefit can be further enhanced by providing a physical barrier, for example a bulkhead or wall 50 separating the circuit board region from the liquid cold plate region. Taken to extreme, the physical barrier could be in the form of an enclosure (such as suggested by dotted line 52) housing the circuit board where the condenser component and electrical connector protrude through one wall of enclosure. As shown in FIG. 12 c, the structure could even completely enclose condenser 20, leaving interface material 48 on the exterior of enclosure 52′.

In FIG. 12 the liquid cold plate mates with the inclined bottom surface of condenser 20. Liquid cold plate 44 is provided with a correspondingly angled upper surface. The circuit board is moved horizontally to engage both electrical connector 46 and liquid cold plate 44. A spring 54 urges the upper surface of the liquid cold plate towards the lower surface of the condenser component to provide good thermal communication at the interface. As with air cooled fins, a liquid cold plate can be used on the lower surface of the condenser, the upper surface, or both.

Although in FIG. 12 the liquid cold plate has an inclined surface, this simply represents a design choice. A cold plate whose upper and lower surfaces are parallel (as is most commonly the case) can be used by inclining the entire cold plate as needed to mate with the inclined surface of the condenser component.

In any embodiment or configuration, the inventive thermal transfer device has a reduced vertical profile when compared to known prior art devices, and provides improved and efficient thermal transfer, particularly for applications providing a limited vertical space by virtue of the invention's configuration.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. 

What is claimed is:
 1. A condenser for use in a thermal transfer device and adapted to be coupled to a reservoir for holding a thermal transfer fluid in at least one of a liquid state and a vapor state, the condenser comprising: an inlet for receiving the thermal transfer fluid in a vapor state from the reservoir; an outlet for returning the thermal transfer fluid to the reservoir in a liquid state; and first and second header spaces; said inlet being positioned at a height relative to the reservoir which is greater than a height of said outlet and being configured to introduce the thermal transfer fluid in said vapor state to said first header space; said outlet being configured to conduct the thermal transfer fluid in said liquid state from said second header space; each of said inlet and said outlet being positioned at a height above a level of the thermal transfer fluid in its liquid state in the reservoir; an array of substantially vertical fins disposed within the condenser; wherein said fins define passages therebetween, said passages opening into said first and second header spaces and permitting the flow of the thermal transfer fluid therethrough.
 2. The condenser of claim 1, wherein said first and second header spaces are separated from each other.
 3. The condenser in claim 1 wherein said first and second header spaces comprise one header space
 4. The condenser of claim 1, wherein said inlet and said outlet form a single conduit.
 5. The condenser of claim 1, wherein said inlet and said outlet are on the same side of said condenser.
 6. The condenser of claim 1, wherein said condenser has a bottom surface positioned so that it slopes in a direction of said outlet to facilitate the flow of the thermal transfer fluid to said outlet when the thermal transfer fluid is in its liquid state.
 7. The condenser of claim 1, wherein each of said fins has a plurality of flutes on at least one side thereof.
 8. The condenser of claim 7, wherein said flutes are on opposing sides of said fins.
 9. The condenser of claim 8, wherein said flutes are disposed in matched pairs on said opposing sides of said fins.
 10. The condenser of claim 8, wherein said flutes are disposed on said opposing sides of said fins in a staggered relationship.
 11. The condenser of claim 1, wherein the depth of said condenser is greater than the height, thereby permitting the thermal transfer device to have a reduced vertical profile.
 12. The condenser of claim 1, further comprising a second plurality of fins on the exterior of said condenser, said second plurality of fins not being in contact with the thermal transfer fluid in either its liquid or vapor state.
 13. The condenser of claim 1, further comprising a liquid cold plate in at least one of above or below the condenser chamber in thermal communication with said chamber.
 14. A thermal transfer device for use in an environment with a small vertical clearance, the device comprising: a reservoir for holding a thermal transfer fluid in a liquid state; a condenser having an inlet for receiving the thermal transfer fluid in a vapor state from said reservoir; an outlet for returning the thermal transfer fluid to said reservoir in the liquid state; and first and second header spaces; said inlet being positioned above said outlet and being configured to introduce the thermal transfer fluid in its vapor state to said first header space; said outlet being configured to conduct the thermal transfer fluid in its liquid state from said second header space; each of said inlet and said outlet being positioned at a height above a level of the thermal transfer fluid in its liquid state in said reservoir; and an array of substantially vertical fins disposed within said condenser; wherein said fins define passages therebetween, said passages opening into said first and second header spaces and permitting the flow of the thermal transfer fluid therethrough; whereby the thermal transfer fluid in its vapor state may enter the condenser through said inlet into said first header space, whereupon it flows through the tops of said passages to contact said fins, where the vapor condenses, whereupon it flows back through the bottom of said passages to said second header space and then to said outlet for return to the reservoir.
 15. The thermal transfer device of claim 14, further comprising a first conduit for conducting the thermal transfer fluid from said reservoir to said inlet.
 16. The thermal transfer device of claim 15, wherein said first conduit is adapted to conduct the thermal transfer fluid in its vapor state from said reservoir to said inlet.
 17. The thermal transfer device of claim 15, further comprising a second conduit for conducting the condensed thermal transfer fluid in its liquid state from said outlet to said reservoir.
 18. The thermal transfer of claim 14, wherein said condenser has a bottom surface positioned so that it slopes in the direction of said outlet to facilitate the flow of the thermal transfer fluid to said outlet when the thermal transfer fluid is in its liquid state.
 19. The thermal transfer device of claim 14, wherein each of said fins has a plurality of flutes on at least one side thereof.
 20. The thermal transfer device of claim 14, further comprising a second plurality of fins on the exterior of said condenser, said second plurality of fins not being in contact with the thermal transfer fluid in either its liquid or vapor state.
 21. The thermal transfer device of claim 14, wherein the depth of said condenser is greater than the height thereof, thereby permitting the thermal transfer device to have a reduced vertical profile.
 22. The thermal transfer device of claim 14, further comprising: means for attaching an external thermal transfer apparatus to the thermal transfer device to provide thermal contact with said condenser, and to provide additional thermal transfer capacity to the thermal transfer device.
 23. The thermal transfer device of claim 22, further comprising a thermal transfer medium applied to the exterior of said condenser to provide thermal conduction between the thermal transfer apparatus and said condenser.
 24. The thermal transfer device of claim 23, wherein said thermal transfer medium is selected from one of a thermally conductive pad, a thermally conductive gel and a thermally conductive grease.
 25. The thermal transfer device of claim 22, wherein said means for attaching includes a spring which urges the external thermal transfer apparatus into contact with said condenser.
 26. The thermal transfer device of claim 22, further comprising a barrier component.
 27. The thermal transfer device of claim 26, wherein said barrier component is one wall of an enclosure.
 28. The thermal transfer device of claim 27, wherein said enclosure substantially surrounds said thermal transfer device.
 29. The thermal transfer device of claim 27, wherein said enclosure substantially surrounds said reservoir of said thermal transfer device. 